Over Molded Carriers such as the Over Molded Pad Array Carrier (OMPAC), the Over Molded Peripheral Chip Carrier (OMPCC), and the Over Molded Pin Grid Array (OMPGA) and their equivalent glob top printed circuit board chip carriers are susceptible to moisture during manufacturing. These integrated circuit packages suffer from "Popcorning" when subjected to heat. This problem is particularly noticeable in surface mount packages using printed circuit boards, which experience higher thermal and mechanical stresses due to the exposure of the entire package to solder reflow temperatures. Typically, these integrated circuit packages are baked prior to solder assembly to remove moisture. Moisture usually penetrates the over mold top or glob top, the substrate, the die or integrated circuit residing between the over mold top or glob top and the substrate, and especially the adhesive used to attach the die to the substrate. The die attach adhesive is usually a hygroscopic material. Exposure of the package to solder reflow temperatures after the die attach adhesive absorbs moisture, causes the rapid expansion of the moisture into water vapor. This causes the die to delaminate from the substrate. Thus the "popcorn" effect.
U.S. Pat. No. 4,866,506 by Nambu Et. Al. discusses a flat plastic-sealed IC device and lead frame in a package that has an opening in the back surface of the package, allowing exposure to the atmosphere and the release of moisture when subjected to heat. This package, also known as the Quad Flat Pack (QFP), is easily manufactured, but leaves the bottom surface of the lead frame exposed to the atmosphere. The QFP does not use a substrate or printed circuit board as in OMPAC, OMPCC, and OMPGA and their glob top equivalents; thus, a different solution is required. The present invention provides a means for releasing moisture in a completely different structure.